Setup has detected SyncBack currently running

Setup has detected that SyncBackPro/SE/Lite/Free is currently running. Please close all instances of it now, then click Ok to continue, or Cancel to exit.

The installer program has
been advised by Windows that the main EXE file for the product in
question is loaded into memory, and the EXE file is thus locked (cannot
be overwritten/updated). Some common reasons for this are:

an instance of the program is open but hidden, possibly because
it is Minimized To Tray. If so, note that the tray icon may be hidden by
Windows due to this syndrome (Windows 7 & later). Remember also that if you have the program
set to Minimize On Close, it will do just that if you click the [X] box
upper right, or right-click the upper-left icon on the title-bar >
Close, or use Alt-F4. The only way to close the program with this option
selected is to click the Exit button (with the door picture) bottom
right.

an instance of the program is running on a Schedule behind the scenes (or, was running and is now locked-up due to a run-time error and cannot self-close)

you have a profile set to run On Login, and it is still running
(possibly minimized to a tray icon, which Windows may then be hiding -
see above)

an instance of the program is running in another user's session
(if you used Fast User Switching or equivalent), and/or as Scheduled by
such a different user

You can check if this is the case by using Windows Task Manager.
Right-click an empty area of Taskbar > Start Task Manager >
Processes tab (not Applications tab) > click Show Processes From All Users
(very important - or hidden instances will remain so) > check for
instances of SyncBackPro.exe (or SyncBackSE.exe, or SyncBackLite.exe or SyncBackFree.exe)
> right-click > End Process. Remember that a hidden instance of
the program may in fact be in mid-run - although forcibly closing such
an instance will usually at worst result in an incomplete copy of a
file, you do so at your own risk.

(Windows 8 introduced an new-style Task Manager that does not have Applications and Processes on separate tabs (though by default they are Grouped By Type). Nor does it suppress processes from other users, but you may need to switch to the Details tab to see them.)

Rebooting the PC may well help,
but bear in mind that if the program is set to Start With Windows, it
very probably will, meaning you may be back where you started. It may be
necessary to manually start the program, unset Start With Windows
(Preferences menu > Options > Easy tab). Then reboot again, and
the program will most likely not be running thereafter unless you have
anything Scheduled and by coincidence the Schedule triggered just after
Windows started.

Another option is to reboot Windows into Safe Mode, then
run the installer. Safe Mode suppresses almost all optional processes
from starting automatically. If you are unsure how to boot into Safe
Mode, please Google (etc.) for instructions specific to your version of
Windows.

Note: please remember that as
'delivered' and as originally installed, SyncBackPro/SE/Lite/Free do not
self-start in any way by any method. If you take no action (and decline the invitation in the
installer to auto-start it once for you), it will sit on your PC for
ever and never run. There are numerous ways you can configure the
program to start, enable automated start-up, and/or configure external
processes to start our software unilaterally. But whatever process
started the program was configured by one or more users at your side
somehow. We cannot remotely identify for you what process started the
program (or is repeatedly re-starting it), except for the above
suggestions and possible workarounds.